1. Field of the Invention
The present invention relates to a gas turbine moving blade platform constructed so as to enhance a cooling performance thereof.
2. Description of the Prior Art
FIG. 6 is a cross sectional view of a representative prior art gas turbine moving blade platform, which is an example of that used for a first stage moving blade. In FIG. 6, numeral 50 designates a platform in its entire form and numeral 51 designates a first stage moving blade. Numeral 52 designates a leading edge passage of the moving blade 51 and cooling passages 53, 54 are in communication with the leading edge passage 52 and extend toward respective side portions of the platform 50. The cooling passages 53, 54 connect to cooling passages 55, 56, respectively, on both side portions and the cooling passages 55, 56 open at a rear end of the platform 50 so that cooling air 70 flows out at the rear end of the platform.
In a front portion of the platform 50, there are provided cooling passages 57 and 58, 59 and 60, respectively, on both sides thereof and these cooling passages 57 to 60 are bored at an angle from a lower surface toward an upper surface of the platform 50 to open at the upper surface so that cooling air is blown therefrom. Also, in a rear portion of the platform 50, there are bored cooling passages 61, 62, 63 which also extend at an angle from the lower surface toward the upper surface of the platform 50 to open at the rear end thereof so that the cooling air is blown therefrom.
Further, in a central portion of the platform 50, there are provided cooling passages 64, 65, 66, 67, 68 and these cooling passages are also bored at an angle from the lower surface toward the upper surface of the platform 50 so that the cooling air is blown from the upper surface, wherein an outlet end portion of each of the cooling passages 64 to 68 is enlarged in a funnel-like shape so that the cooling air is diffused on the upper surface.
FIG. 7 is a cross sectional view taken on line C--C of FIG. 6, wherein the cooling passages 55, 56 are provided in both side portions of the platform 50 and the cooling passage 67 is bored at an angle from the lower surface toward the upper surface of the platform 50.
FIG. 8 is a cross sectional view taken on line D--D of FIG. 6, wherein there are provided the cooling passage 55 extending from the front portion toward the rear portion of the platform 50 to open at the rear end and the inclined cooling passages 57, 64 to 68 extending so that the cooling air is blown therethrough rearwardly and upwardly, respectively.
In the platform 50 constructed as above, cooling air which has been supplied into the moving blade 51 through the leading edge passage 52 flows portionally into the cooling passages 55, 56 for cooling both side portions of the platform 50 and to then flow out of the rear end of the platform 50. Also, the cooling passages 57 to 60, and 61 to 63, respectively, are provided in the front and rear portions of the platform 50 so that cooling air is introduced thereinto from the lower surface of the platform 50 to flow out of the upper surface of the front and rear end portions of the platform 50. Further, the cooling passages 64 to 68 are provided in the central portion and cooling air flows therethrough from the lower surface of the platform 50 so as to flow out of the upper surface thereof. Thus, the entire portion of the platform 50 is cooled by the cooling air flowing therein and flowing out thereof.
In the representative prior art gas turbine moving blade platform as described above, there are provided cooling passages 55, 56 which are main cooling passages extending linearly and in addition thereto, there are provided the multiplicity of cooling passages 57 to 60, 61 to 63, etc., which pass through the platform 50 at an angle and thus constitute comparatively long inclined routes. Hence, in the platform 50, there are provided many such cooling air supply passages and thus processing of the platform itself becomes complicated and such a cooling structure for the platform is desired which can be made simpler and still has an excellent cooling effect to cool uniformly the entire portion of the platform including peripheral side portions thereof where there is a severe thermal influence.